Environment Editor, The Sydney Morning Herald

Saving begins at home ... the CSR house has an eight-star energy performance rating.

AUSTRALIANS wondering how to limit their contribution to climate change don't have to look beyond the front gate, says Tony Isaacs, a specialist in sustainable buildings.

Housing ''is the biggest investment in your life,'' Isaacs says. ''You can do something good for the environment and it's good for you.''

Since May last year, new houses in Australia are required to have a minimum six-star energy performance rating. Experts and parts of the building industry say that bar can easily be cleared without blowing the budget.

''The minimum standards overseas are between six and eight stars, so we've basically only caught up to the bottom end,'' Mr Isaacs said.

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The CSR house, located in Schofields on the sprawling north-western fringe of Sydney, is the latest example of the energy efficient options becoming available. Opened last month, the eight-star rated house was developed by building supplier CSR as part of the national Co-operative Research Centre for Low Carbon Living, using expertise from the Commonwealth Scientific and Industrial Research Organisation, universities and industry partners.

The principal architect, Gareth Cole from The Ecologie Group, says the 250-square-metre house was designed to cater to conventional buyers but uses 75 per cent less energy than similar homes built a decade or so ago. Compared with the six-star standard, the heating and cooling load is 45 per cent lower, with the difference expected to widen once information gathered from 140 data sensors is analysed.

Many of the features - such as metre-wide eaves and ventilation and zoning to suit the seasons - are well known but poorly applied, said Ray Thompson, general manager of innovation at CSR.

''Australia has been pretty atrocious … in how we've ignored energy efficiency as an aspect of how we build houses,'' he said.

To get to eight stars, the three- to four-bedroom house cost about $325,000 to build, or about $25,000 more than required for a six-star rating Mr Thompson says.

About $10,000 of those extra dollars went into the high-tech ''thermal broken'' double glazing, which curtails energy leakage through windows. A smart ventilation system added about $2000. These and other costs, though, should decline as industry develops scale and technology improves, he said.

The Melbourne research fellow Dr Trivess Moore conducted a study for RMIT University that suggests the dollar gap may be even narrower.

Modelling for 80 detached homes in Victoria found the average cost to lift the energy rating from six to eight stars was $8154, based on an average building cost of about $180,000. The payback period based on a low-energy price future was about 20 years, with the level falling to 14 years based on higher energy costs, he found. For perspective, most houses are likely to last many decades.

Dr Moore identified in his PhD thesis that the costs of lifting energy ratings typically fall far short of levels claimed by the construction industry.

For instance, the Master Builders Association of Victoria estimated the cost of moving from a five-star to a six-star rating would be between $5000 and $10,000, while data compiled by Tony Isaacs and Constructive Concepts estimated the actual tally to be about $2300 on average.